1. Field of the Invention
The present invention relates to an occupant condition determining apparatus using an infrared ray sensor such as a pyroelectric type sensor, and more particularly to an occupant condition determining apparatus with a function for determining the conditions of occupants in a room (i.e., the number, the positions, and the activities thereof).
2. Description of the Related Art
Recently, an occupant sensing apparatus has become practical and useful. This type of apparatus senses infrared rays corresponding to a body temperature which are emitted from a human body by using an infrared ray sensor. The apparatus detects the intensity variation of the infrared rays in a predetermined detecting region in order to determine whether any occupant is present or absent in the predetermined detecting region. The occupant sensing apparatus is used for determining the conditions of occupants in a room, such as the number, the positions and the activities of the occupants, and hence can be applied to an air conditioner or the like.
Japanese Laid-Open Patent Publication No. 1-147241 discloses an air conditioner having a function for determining the number of occupants in a room. An infrared ray sensor is rotated so as to scan a room, and the number of large changes in the output of the sensor is counted. The count indicates the number of occupants.
Japanese Laid-Open Patent Publication No. 2-52201 discloses an occupant position detector for determining the positions of occupants in a room. Prescribed regions of a room are sequentially sensed, and an occupant detection signal is produced when an infrared ray sensor detects a change in the intensity of infrared rays corresponding to a body temperature. A region for which the occupant detection signal is produced is determined to include an occupant. Such determination is applied to the control of the wind direction depending on the positions of occupants. For example, during a heating operation of an air conditioner, a cold wind at the beginning of the heating operation is prevented from being directed to occupants.
Japanese Laid-Open Patent Publication No. 2-93232 discloses an air-conditioning control apparatus having a function for determining the activities of occupants in a room. The activities of occupants in a room are determined by counting the number of changes in the intensity of infrared rays. For the purpose of air-conditioning control, for example, if the number of intensity changes is large, the occupants are determined to be actively moving. According to such determination, the set temperature is lowered, thereby improving the feeling temperature for the occupants.
However, the conventional occupant sensing apparatus as described above has the following drawbacks.
As to the determination of the number of occupants, the output signal of the employed infrared ray sensor is one-dimensional. Therefore, if a plurality of occupants exist along the detecting direction, it is erroneously determined that there is one occupant. In addition, the thermal environment and the quality of air (e.g., the CO.sub.2 concentration of the room) to be controlled in the air conditioning are largely influenced by the number of occupants in the room. If the above erroneous determination is made, comfortable air conditions cannot always be realized.
As to the determination of the positions of occupants, some position, posture, or movement leads to an erroneous determination that there exists an occupant on a region, while there is actually no occupants on the region. Because of such erroneous determination on the positions, comfortable air-conditions for each occupant cannot be realized.
As to the determination of the activities of occupants, such activities are determined only based on the number of intensity changes of infrared rays. If there are many occupants in a specific region, for example, the number of intensity changes increases. Therefore, even if each occupant is not so actively moving, it is sometimes determined that there are many movements. In other words, the number of intensity changes largely depends on the number of occupants in the specific region, so that the activities of the occupants cannot separately and accurately be determined. Therefore, it is impossible to perform the control for more comfortable air-conditions in accordance with the conditions of the respective occupants.